Anticorrosion coating composition in aqueous dispersion comprising an organic titanate and/or zirconate

ABSTRACT

Anticorrosion coating compositions for metallic parts based on particulate metal in aqueous dispersion are described. The compositions include an organic titanate or zirconate compatible in aqueous phase or in organic phase, an optional silane-based binder, and water. Also described are methods of forming anticorrosion coatings for metallic parts obtained from the noted coating compositions as well as a metallic substrate provided with the anticorrosion coating. The anticorrosion coatings exhibit excellent corrosion resistance upon baking at temperatures greater than 180° C. and up to 350° C.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a continuation-in-part (CIP) application of U.S. applicationSer. No. 10/589,040 filed Aug. 10, 2006 now abandoned, which is aNational Phase of PCT/IB2005/000488, filed Feb. 10, 2005, which claimspriority upon France Patent Application 0401349 filed Feb. 11, 2004.

FIELD OF THE INVENTION

The present invention relates to anticorrosion coating compositions formetal parts. The compositions are based on particulate metal in aqueousdispersion comprising an organic titanate or zirconate compatible inaqueous phase or in organic phase, an optional a silane-based binder,and water. The compositions are heated at particular temperatures toform coatings that exhibit excellent resistance to corrosion.

BACKGROUND OF THE INVENTION

A wide array of anticorrosion coatings are known in the art. One groupof such coatings contain organic titanates and/or organic zirconates.Although satisfactory in certain regards, many of these compositions arefree from water and so precautions must be undertaken to avoid exposureor contamination with water. Chelation techniques are known in which thetitanates and/or zirconates can be modified to thereby allow theirincorporation in aqueous systems. However, a need remains for a strategyin which such agents can be incorporated into an aqueous compositionwhich then enables their subsequent use in an anticorrosion composition.

SUMMARY OF THE INVENTION

The difficulties and drawbacks associated with previously known systemsare addressed in the present methods for forming coated metallicsubstrates having anticorrosion coatings, the resulting anticorrosioncoatings, and the compositions utilized for forming such coatings.

In one aspect, the present invention provides a method for forming acoated metallic substrate having an anticorrosion coating. The methodcomprises obtaining a coating composition including from 0.3% to 24% byweight of at least one agent selected from the group consisting oforganic titanate, organic zirconate and mixtures thereof, from 10% to40% by weight of a particulate metal or a mixture of particulate metals,from 1% to 25% by weight of a silane-based binder, and water, whereinthe sum of the organic titanate and/or zirconate agent and of thesilane-based binder is from 5 to 25% by weight. The method alsocomprises forming a coating layer of the coating composition on ametallic substrate. And, the method additionally comprises subjectingthe coating layer to a baking operation at a temperature greater than180° C. and up to 350° C. by supply of thermal energy to thereby formthe anticorrosion coating.

In another aspect, the present invention provides an anticorrosioncoating resulting from baking a particular coating composition at atemperature between greater than 180° C. and up to 350° C. The coatingcomposition comprises a coating composition including from 0.3% to 24%by weight of at least one agent selected from the group consisting oforganic titanate, organic zirconate and mixtures thereof, from 10% to40% by weight of a particulate metal or a mixture of particulate metals,from 1% to 25% by weight of a silane-based binder, and water, whereinthe sum of the organic titanate and/or zirconate agent and of thesilane-based binder is from 5 to 25% by weight. The resulting coatingexhibits resistance to corrosion from exposure to saline mist for atleast 200 hours without formation of red rust.

In yet another aspect, the present invention provides a coatingcomposition including from 0.3% to 24% by weight of at least one agentselected from the group consisting of organic titanate, organiczirconate and mixtures thereof, from 10% to 40% by weight of aparticulate metal or a mixture of particulate metals, from 1% to 25% byweight of a silane-based binder, and water, wherein the sum of theorganic titanate and/or zirconate agent and of the silane-based binderis from 5 to 25% by weight.

In still another aspect, the present invention provides an aqueouscomposition of C₁-C₈ tetraalkyl titanate and/or zirconate, adapted foruse in a coating composition for a metallic substrate in aqueousdispersion. The composition comprises the following proportions(percentages by weight): water-soluble organic solvent in an amount from0 to 20%; silane-based binder in an amount from 20 to 50%, the silanehaving at least one hydrolysable hydroxyl function; at least one agentselected from the group consisting of C₁-C₈ tetraalkyl titanate, C₁-C₈tetraalkyl zirconate and mixtures thereof in an amount from 5 to 25%,compatible in organic phase; and water in an amount sufficient toproduce 100%.

In another aspect, the present invention provides a method forpretreating a substrate prior to receiving an adhesive or coating. Themethod comprises providing a composition comprising in the followingproportions (percentages by weight): water-soluble organic solvent in anamount from 0 to 20%, silane-based binder in an amount from 20 to 50%the silane having at least one hydrolysable hydroxyl function, at leastone agent selected from the group consisting of C₁-C₈ tetraalkyltitanate, C₁-C₈ tetraalkyl zirconate and mixtures thereof in an amountfrom 5 to 25% compatible in organic phase, and water in an amountsufficient to produce 100%. The method also comprises applying a coatingof the composition to the substrate, to thereby pretreat the substrate.

In another aspect, the present invention provides a method for sealing asubstrate or coated substrate. The method comprises providing asubstrate or coated substrate. The method also comprises providing acomposition comprising in the following proportions (percentages byweight): water-soluble organic solvent in an amount from 0 to 20%,silane-based binder in an amount from 20 to 50% the silane having atleast one hydrolysable hydroxyl function, at least one agent selectedfrom the group consisting of C₁-C₈ tetraalkyl titanate, C₁-C₈ tetraalkylzirconate and mixtures thereof in an amount from 5 to 25% compatible inorganic phase, and water in an amount sufficient to produce 100%. Themethod additionally comprises applying a coating of the composition onthe substrate, to thereby seal the substrate or coated substrate.

In still another aspect, the present invention provides a method forpassivating a substrate of steel, zinc, aluminium, or steel having azinc-based coating. The method comprises providing a substrate selectedfrom the group consisting of steel, zinc, aluminium, and steel having azinc-based coating. The method also comprises providing a compositioncomprising in the following proportions (percentages by weight):water-soluble organic solvent in an amount from 0 to 20%, silane-basedbinder in an amount from 20 to 50% the silane having at least onehydrolysable hydroxyl function, at least one agent selected from thegroup consisting of C₁-C₈ tetraalkyl titanate, C₁-C₈ tetraalkylzirconate and mixtures thereof in an amount from 5 to 25% compatible inorganic phase, and water in an amount sufficient to produce 100%. And,the method also comprises applying a coating of the composition on thesubstrate, thereby passivating the substrate.

In still another aspect, the invention provides a method for improvingthe adhesion of coatings or adhesives in aqueous phase. The methodcomprises forming a composition comprising in the following proportions(percentages by weight): water-soluble organic solvent in an amount from0 to 20%, silane-based binder in an amount from 20 to 50% the silanehaving at least one hydrolysable hydroxyl function, at least one agentselected from the group consisting of C₁-C₈ tetraalkyl titanate, C₁-C₈tetraalkyl zirconate and mixtures thereof in an amount from 5 to 25%compatible in organic phase, and water in an amount sufficient toproduce 100%. The method also comprises adding the composition to acoating or adhesive to thereby improve the resulting adhesion of thecoating or adhesive.

As will be realized, the invention is capable of other and differentembodiments and its several details are capable of modifications invarious respects, all without departing from the invention. Accordingly,the drawings and description are to be regarded as illustrative and notrestrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of infrared (IR) spectra of several preferredembodiment compositions heated and cured at different temperatures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the present invention and its various preferredembodiments, it is instructive to consider several terms used herein.The expressions “titanate(s) compatible in organic phase” and“zirconate(s) compatible in organic phase” are understood as meaningevery organic titanate and zirconate not compatible with water. That is,these terms refer to such titanate(s) and/or zirconate(s) that are notsoluble in an aqueous composition and which in addition are sensitive tomoisture and to water and which are thus prone to undergo a hydrolysisreaction.

In addition, the expressions “titanate(s) compatible in aqueous phase”and “zirconate(s) compatible in aqueous phase” are understood as meaningevery organic titanate and zirconate compatible with water. That is,these terms refer to such titanate(s) and/or zirconate(s) that aresoluble, emulsifiable, or dispersible in an aqueous composition. Theseare generally organic titanates and organic zirconates which have beenstabilized by chelation. They are likewise referred to as “chelated(organic) titanate(s)” and “chelated (organic) zirconate(s)”.

The organic titanates, as well as the organic zirconates, compatible inorganic phase can be used in anhydrous compositions as catalysts,reticulating agents, surface-treatment agents, adhesion promoters oranticorrosion agents. However, these organic titanates, as well as theorganic zirconates, have the disadvantage of being very sensitive towater and to moisture inasmuch as they are hydrolysed very rapidly. Forexample, in the case of the hydrolysis of tetra-n-butyl titanate, thefollowing reactions occur:

1) Conversion of the Organic Titanate to Hydrated Titanium OxideTi(OH)₄:Ti(OC₄H₉)₄+4H₂O→Ti(OH)₄+4C₄H₉OH2) Then, Formation of Titanium Dioxide TiO₂:Ti(OH)₄→TiO₂+2H₂O

In order to avoid the formation of titanium dioxide or of zirconiumdioxide, the titanates and zirconates compatible in organic phase mustthus be employed under rigorously anhydrous conditions. Consequently,the preparation of anhydrous compositions comprising a titanate or azirconate compatible in organic phase is accompanied by veryconstraining handling precautions in order to avoid the hydrolysis ofthe organic titanate to titanium dioxide on contact with air, moistureor traces of water.

The moisture resistance of titanates or zirconates compatible in organicphase can be improved by substituting two alkoxy groups by chelatingagents. These chelating agents contain functional groups containingoxygen or nitrogen atoms which happen to stabilize the organic titanateor zirconate. These organic titanates or zirconates in chelated form canlikewise be soluble in water, preferably in the presence of a weak acidof the acetic acid type. For example, U.S. Pat. No. 4,495,156 describestitanates in aqueous chelated form (TYZOR® AA which is a titanatecompatible in organic phase, TYZOR® LA and TYZOR® TE which are titanatescompatible in aqueous phase) which provide for improved adhesion to asubstrate by a composition comprising such titanates.

The hydrolysis rate of the organic titanates and zirconates depends onthe size and the complexity of the alkyl group. Generally, as the sizeof the alkyl group increases, the hydrolysis rate decreases. This is thereason why the organic titanates and zirconates in chelated form areless sensitive to hydrolysis than tetraalkyl titanates or tetra-alkylzirconates.

U.S. Pat. No. 4,224,213 describes coating compositions comprising ashort chain alkyl silicate of formula Si(OR)₄, a short chain alkyltitanate or zirconate and zinc powder. This coating composition isreticulated by reaction of the silicate and the titanate with moisturefrom the air. The examples of this patent note that the addition ofsilicate allows the moisture resistance of organic titanates to beimproved. This coating composition is an organic composition which doesnot contain any water. The silicate, contrary to the silane, does notallow the adhesion of a composition comprising the silicate to asubstrate.

EP Patent 0 808 883 describes an aqueous coating composition based onparticulate metal, free from chromium, intended to be applied to asubstrate. This composition, once applied to the substrate, undergoeshardening in heat in order to provide the substrate with protectionagainst corrosion. In order to increase the corrosion resistance of thiscoated substrate, the coated substrate can optionally be coated with asupplementary layer comprising, for example, a silica material.

Surprisingly, the present invention is based upon a discovery thatorganic titanates and/or organic zirconates can be incorporated into anaqueous composition regardless of whether the organic titanates and/orzirconates are in chelated or non-chelated form and compatible or notcompatible in aqueous phase. The invention is also based upon adiscovery that application to a metallic substrate of an aqueous coatingcomposition based on particulate metal comprising organic titanatesand/or organic zirconates provides improvement in the resistance tocorrosion of the substrate. Due to the excellent anticorrosionproperties, a substrate coated by such a composition does not need anysupplementary layer of anticorrosion coating. In addition, a coating isobtained that exhibits sufficient flexibility and resistance to shocks,which is particularly advantageous for anticorrosion coatings for screwsand other metal fasteners.

The present invention relates to an anticorrosion coating compositionfor metal parts based on particulate metal in aqueous dispersion. Thecoating composition preferably comprises from about 0.3% to about 24% byweight of an organic titanate and/or zirconate, from about 10% to about40% of a particulate metal or a mixture of particulate metals, fromabout 1% to about 25% of a silane-based binder, and water in an amountsufficient for 100%; with the condition that the sum of the organictitanate and/or the organic zirconate and of the silane-based binder isbetween 5 and 25%. Generally the compositions comprise water in anamount of from about 35% to about 85% by weight.

In the preferred embodiment compositions, the organic titanate/zirconatecontent and silane based-binder content are such that the organictitanate/zirconate content is between 0.3 to 24% by weight, the silanebased-binder content is between 1 to 25% by weight, and the sum oforganic titanate/zirconate content and the silane based-binder contentis between 5 to 25% by weight. This means that although the minimalorganic titanate/zirconate content is 0.3% by weight and the minimalsilane based-binder content is 1% by weight, the composition mustcomprise sufficient amounts of one or the other such that the minimal(organic titanate/zirconate and silane based-binder) content is 5% byweight. Similarly, although the maximum organic titanate/zirconatecontent is 24% by weight and the maximum silane based-binder content is25% by weight, the composition must not comprise high amounts of the twosince the maximum (organic titanate/zirconate and silane based-binder)content is 25% by weight.

More preferably, the compositions comprise from about 0.5% to about 19%by weight, with respect to the total weight of the composition, oforganic titanate and/or zirconate and from about 1% to about 20% byweight, with respect to the total weight of the composition, ofsilane-based binder, with a condition that the sum of organic titanateand/or zirconate and silane-based binder is between about 7% and about20% by weight, with respect to the total weight of the composition.

The organic titanates can be selected from the group comprising thepreviously noted organic titanates compatible in organic phase and theorganic titanates compatible in aqueous phase.

The titanates compatible in organic phase are preferably C₁-C₈tetraalkyl titanates which can be represented by the following formula(I′):

in which R1, R2, R3 and R4 independently represent an optionallysubstituted C₁-C₈ alkyl radical. The C₁-C₈ tetraalkyl titanate ispreferably selected from the group comprising tetraethyl titanate (TET,Ti(OC₂H₅)₄), tetra-n-butyl titanate (T_(n)BT, Ti(OC₄H₉)₄) octyleneglycol titanate (OGT, Ti(O₂C₈H₁₇)₄), and combinations thereof.

The organic titanates compatible in organic phase can likewise beorganic titanates in chelated form not compatible with water. Asexamples of organic titanates in chelated form not compatible with water(compatible in organic phase), it is especially possible to cite thosemarketed by Dupont de Nemours under the name TYZOR® AA (titaniumacetylacetonate) or TYZOR® DC (diisopropoxy bisethylacetoacetatotitanate).

The titanates compatible in aqueous phase are preferably chelatedtitanates, which can be represented by the following general formula(II′):

in which R and R′ independently of one another represent an optionallysubstituted C₁-C₈ alkyl radical, X and X′ independently represent afunctional group comprising an oxygen or nitrogen atom, and Y and Y′independently represent a hydrocarbon chain having 1 to 4 carbon atoms.X and X′ preferably represent an amino or lactate radical.

The organic titanate in chelated form compatible in aqueous phase ispreferably selected from the group comprising the triethanolaminetitanates (TYZOR® TE and TEP marketed by Dupont de Nemours). As anexample of organic titanates in chelated form compatible in aqueousphase, it is likewise possible to cite those marketed by Dupont deNemours under the name TYZOR® TA (alkanolamine titanate in chelatedform) and TYZOR® LA (chelate of titanate and lactic acid).

The organic zirconate can be selected from the group comprising thepreviously noted zirconates compatible in organic phase and thezirconates compatible in aqueous phase.

The organic zirconates compatible in organic phase are preferably C₁-C₁₀tetraalkyl zirconates, which can be represented by the following formula(I):

in which R1, R2, R3 and R4 independently represent an optionallysubstituted C₁-C₁₀ alkyl radical. The C₁-C₁₀ tetraalkyl zirconate ispreferably selected from the group comprising tetra-n-propyl zirconateand tetra-n-butyl zirconate.

The organic zirconates compatible in organic phase can likewise beorganic zirconates in chelated form not compatible with water. As anexample of an organic zirconate in chelated form not compatible withwater (compatible in organic phase), it is especially possible to citethose marketed by Dupont de Nemours under the name TYZOR® ZEC (chelateddiethyl citrate zirconate).

The organic zirconates compatible in aqueous phase are preferablychelated zirconates which can be represented by the following generalformula (II):

in which R and R′ independently of one another represent an optionallysubstituted C₁-C₁₀ alkyl radical, X and X′ independently represent afunctional group comprising an oxygen or nitrogen atom, and Y and Y′independently represent a hydrocarbon chain having 1 to 4 carbon atoms.X and X′ preferably represent an amino radical.

The chelated organic zirconate can preferably be triethanolaminezirconate (TYZOR® TEAZ marketed by Dupont de Nemours). As an example ofan organic zirconate in chelated form compatible in aqueous phase, it islikewise possible to cite that marketed by Dupont de Nemours under thename TYZOR® LAZ (chelate of zirconate and lactic acid).

The particulate metal of the coating composition can be selected fromthe group comprising metallic pigments such as aluminium, manganese,nickel, titanium, stainless steel, zinc, their alloys, as well as theirmixtures. The particulate metal is preferably selected from zinc andaluminium, as well as their alloys and their mixtures or their alloyswith manganese, magnesium, tin or Galfan. Galfan refers to an alloycommercially available under that designation. Galfan alloys are aeutectic alloy of 95% zinc, nearly 5% aluminum, and a trace ofmischmetal (rare earth elements) as per ASTM B750. Galfan is availablefrom a wide array of suppliers. The particulate metal present in thecomposition is preferably in powder form, different homogeneous orheterogeneous geometric structures, especially spherical, lamellar,lenticular forms or other specific forms. The particulate metalpreferably has a particle size of less than 100 μm, and more preferablyless than 40 μm.

When the particulate metal is an alloy or a mixture of zinc andaluminium, the aluminium can optionally be present in very smallquantities, for example 1 to 5% by weight of the particulate metal,while at the same time nevertheless providing a coating of shinyappearance. In certain embodiments, the preferred coating compositionincludes zinc and aluminum flakes. These flakes can serve as sacrificialagents to further protect the substrate against corrosion. Typically,the aluminium represents at least 10% by weight of the particulatemetal, thus the weight ratio of the aluminium to the zinc is of theorder of 1:9. On the other hand, for reasons of economy, the aluminiumdoes not represent more than approximately 50% by weight of the totalzinc and aluminium, so that the weight ratio of the aluminium to thezinc can reach 1:1. The content of particulate metal of the coatingcomposition will not exceed approximately 40% by weight of the totalweight of the composition in order to maintain the best coatingappearance and will typically represent at least 10% by weight in orderto obtain a shiny coating appearance. In certain embodiments of theinvention, the coating composition can contain relatively highconcentrations of pigments, such as from about 10% to about 40% byweight based upon the weight of the liquid composition. Surprisingly,the adhesion of the coating to an underlying substrate is remarkablygood. Furthermore, it is believed that the adhesion of the preferredembodiment coatings to substrates is increased by use of relatively highcuring temperatures as explained herein.

The metal or the component containing the metal, can contain in minorquantity of one or more solvents, for example dipropylene glycol and/orwhite spirit, especially when the metal has been prepared in lamellarform. The particulate metals provided in combination with solvents aretypically used in the form of pastes, which can be used directly withother ingredients of the composition. However, the particulate metalscan likewise be used in a dry form in the coating composition.

The silane-based binder preferably comprises a silane including at leastone hydrolysable function in hydroxyl function selected from a C₁-C₄,preferably C₁-C₂, alkoxy radical. The silane preferably includes threehydrolysable functions in hydroxyl function, preferably identical. Thesilane can additionally include an epoxy(oxirane) function, which favorsthe reticulation and adhesion to the substrate. The term “hydrolysablefunction in hydroxyl function” as used herein refers to any chemicalfunction capable of reacting with water in order to be converted into ahydroxyl function, i.e. OH.

The silanes, in the compositions of the present invention, serve asbinding agents. They likewise allow the coating bath to be stabilizedagainst harmful autogenous reaction(s). It is believed that the silanebinds and passivates the particulate metal, to thereby improve thestability of the bath of the coating composition. In addition, thatsilane binding agent improves the adhesion of the coating and itsresistance to corrosion. The silane preferably represents from about 3to about 20% by weight of the total weight of the composition. However,the silane based binder can be used in a concentration of from about 1to 25%.

The silane is preferably easily dispersed in the aqueous medium and is,preferably, soluble in such a medium. The silane used is preferably asilane with an epoxy function selected from di- or trimethoxysilane withan epoxy function and di- or triethoxysilane with an epoxy function, aswell as their mixtures, in particular likebeta-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane,4-(trimethoxysilyl)butane-1,2-epoxide,gamma-glycidoxypropyltrimethoxysilane orgamma-glycidoxypropyltriethoxysilane.

If the organic titanate and/or zirconate used is an organic titanateand/or zirconate compatible in aqueous phase, the silane is preferablyintroduced in quantities such that the proportions by mass, in the finalcomposition, of organic titanate and/or zirconate compatible in aqueousphase: silane are between 95:5 and 5:95.

The anticorrosion composition can be prepared by mixing an organicphase, especially comprising the silane and the particulate metal, withan aqueous phase, especially comprising water and the silane. Theorganic titanate and/or zirconate compatible in aqueous phase can beintroduced either into the aqueous phase or into the organic phase.

When the organic titanate and/or zirconate compatible in aqueous phaseis introduced into the organic phase, it is possible to substitute thesilane, normally present in the organic phase, by this organic titanateand/or zirconate. The proportions by mass, expressed in dry parts, oforganic titanate and/or zirconate and of silane are preferably between1:19 and 2:1, more preferably between 1:16 and 1:8.

When the organic titanate and/or zirconate compatible in aqueous phaseis introduced into the aqueous phase, it is preferably firstco-hydrolysed with the silane, normally present in the aqueous phase.The mass proportions of organic titanate and/or zirconate and of silaneduring the co-hydrolysis are preferably between 0.12 and 0.36, expressedin dry parts. The optimal conditions for the co-hydrolysis are obtainedfor a ratio by mass of 0.24 titanate and/or zirconate for 1 silane, theratios being expressed in dry parts.

In order to co-hydrolyse the organic titanate and/or zirconate and thesilane, the organic titanate and/or zirconate is introduced into thesilane, in an appropriate ratio, then they are co-hydrolysed by additionof 200 to 500% of water. It is believed that the duration of theco-hydrolysis reaction, that is to say the waiting time which followsthe addition of the water, for example 30 or 90 min, does not have anyinfluence on the properties of the co-hydrolysate obtained. If, insteadof co-hydrolysing the silane and the organic titanate and/or zirconatecompatible in aqueous phase, they are each hydrolysed separately, lesssatisfactory results are obtained in terms of product stability.

The addition of organic titanate and/or zirconate compatible in aqueousphase in the aqueous phase of the anticorrosion composition improves theanticorrosion properties of this composition more than if this titanateand/or zirconate had been added in the organic phase.

If the organic titanate and/or zirconate used is a titanate and/orzirconate compatible in organic phase, preferably a C₁-C₈ tetraalkyltitanate and/or zirconate, the silane is preferably introduced inquantities such that the proportions by mass, in the final composition,of titanate and/or zirconate compatible in organic phase/silane arebetween 60/40 and 5/95, and preferably between 50/50 and 10/90.

The liquid medium of the coating composition is virtually always wateror a combination of water and organic solvent. Other solvents canoptionally be used but, preferably, only in very small quantities.Typically, the compositions comprise 28 to 65% by weight of water, withrespect to the total weight of the composition. In other embodiments,the compositions comprise water in an amount of from about 35% to about85% by weight.

According to a preferred embodiment of the invention, the coatingcomposition additionally comprises 1 to 30% by weight of organic solventor of a mixture of organic solvents, with respect to the total weight ofthe composition. The organic solvents are preferably selected from thegroup comprising glycolic solvents such as glycol ethers, in particulardiethylene glycol, triethylene glycol and dipropylene glycol, acetates,propylene glycol, polypropylene glycol, nitropropane, alcohols, ketones,propylene glycol methyl ether, 2,2,4-trimethyl-1,3-pentanediolisobutyrate (texanol), white spirit, as well as their mixtures.

Dipropylene glycol is particularly preferred, especially for reasons ofeconomy and for protection of the environment. The quantity of solventsis preferably less than 25% by weight, even more preferably less than16% by weight, with respect to the total weight of the composition. Whenthe metallic particles have been prepared in lamellar form in a solvent,the particulate metal resulting can be in the form of a paste. Theparticulate metal can then form a part of the organic solvent of thecomposition according to the invention.

According to a preferred embodiment of the invention, the coatingcomposition additionally comprises 0.1 to 7% by weight of molybdenumoxide, with respect to the total weight of the composition. The presenceof molybdenum oxide MoO₃ in the anticorrosion coating composition allowscontrol of the sacrificial protection exerted by the particulate metalin suspension in the composition to be improved. The molybdenum oxideMoO₃ is preferably used in an essentially pure orthorhombic crystallineform having a content of molybdenum of greater than approximately 60% bymass. Preferably, the molybdenum oxide MoO₃ will be used in theanticorrosion compositions in the form of particles of dimensions ofbetween 5 and 200 μm.

According to a preferred embodiment of the invention, the coatingcomposition additionally comprises 0.5 to 10% by weight of a reinforcingagent selected from the group comprising yttrium, zirconium, lanthanum,cerium, praseodymium, in the form of oxides or of salts. The reinforcingagent of the composition is preferably yttrium oxide Y₂O₃ or ceriumchloride. The reinforcing agent of the composition can preferably becombined with the abovementioned molybdenum oxide, in a mass ratio asfollows: 0.25<reinforcing agent:MoO₃<20; preferably 0.5<reinforcingagent:MoO₃<16; and most preferably 0.5<reinforcing agent:MoO₃<14.

According to a preferred embodiment, the coating compositionadditionally comprises a corrosion inhibitor pigment or corrosioninhibitor pigments such as the tri- or polyphosphate of aluminium,phosphates, molybdates, silicates and borates of zinc, strontium,calcium, barium and their mixtures, at levels on the order of about 0.2to 4% by weight, with respect to the total weight of the coatingcomposition.

The coating composition according to the invention can additionallycomprise a thickening agent. The thickening agent is preferably selectedfrom the group comprising cellulosic derivatives such ashydroxymethylcellulose, hydroxyethylcellulose, hydroxy-propylcellulose,cellulose acetobutyrate, xanthan gum, associative thickeners ofpolyurethane or acrylic type, silicates such as optionally treatedsilicates of magnesium and/or of lithium or organophilic clays as wellas their mixtures. The content of thickening agent is typically lessthan 7% by weight with respect to the total weight of the composition,and preferably between 0.005 and 7% by weight with respect to the totalweight of the composition.

The coating composition according to the invention can likewise comprisea wetting agent, in a content preferably less than 4% by weight, andmore preferably between 0.1 and 4% by weight, with respect to the totalweight of the composition.

The composition according to the invention can also comprise a pHstabilizer such as boric acid, metaboric acid, tetraboric acid and boronoxide or boron salts. The composition can comprise, with respect to thetotal weight of the composition, 0.1 to 10% by weight, preferably 0.2 to5% by weight and most preferably 0.4 to 0.8% by weight of pH stabilizer.

The composition can likewise comprise a pH modifier, generally selectedfrom oxides and hydroxides of alkali metals, preferably lithium andsodium, the oxides and the hydroxides of metals belonging to groups IIAand IIB of the Periodic Table, such as the compounds of strontium,calcium, barium, magnesium and zinc. The pH modifier can likewise be acarbonate or a nitrate of the abovementioned metals.

The composition according to the invention can likewise comprisephosphates, substituents containing phosphorus, such as ferrophosphate(pigment), non-organic salts, in quantities less than 2% by weight withrespect to the weight of the composition.

The composition according to the invention is preferably free fromchromium VI. The composition can, however, contain chromium in solubleor non-soluble form such as, for example, metallic chromium or chromiumof oxidation state III.

The composition has good stability on storage, confirming the protectiverole of the silane towards a harmful reaction of the particulate metalwith other ingredients of the composition. The silane likewise allowsorganic titanate to be stabilized.

The present invention likewise relates to the coating obtained byapplication of the coating composition according to the invention to asubstrate, preferably by spraying, soaking-draining orsoaking-centrifugation. The term “soaking-draining” refers to atechnique in which a substrate or item to receive a layer or coating ofthe liquid composition is immersed in a bath or other vessel containingthe composition, at least partially removed from the bath, and excessliquid composition on the substrate or item allowed to drain or dripfrom the substrate and return to the bath. The term“soaking-centrifugation” refers to a technique in which a substrate oritem to receive a layer or coating of the liquid composition is immersedin a bath or other vessel containing the composition, at least partiallyremoved from the bath, and then subjected to one or more centrifugationoperations to remove excess liquid from the substrate or item. Thepresent invention includes other techniques for applying the liquidcoating composition and/or removing excess composition therefrom and inno way is limited to these particular techniques or operations.

The coating layer is then subjected to a baking or curing operation,preferably at a temperature of between 180° C. and 350° C., morepreferably greater than 180° C. to 350° C., more preferably between 240°C. and 350° C., and most preferably between 240° C. and 330° C., forapproximately 10 to 60 minutes, by supply of thermal energy, such as byconvection or infrared, or for approximately 30 seconds to 5 minutes byinduction for example. It will be appreciated that the present inventionincludes a wide range of techniques for baking and/or curing thecomposition. As further explained herein, it is preferred to bake orcure a coating of the preferred embodiment composition at the notedtemperatures in order to obtain the excellent and surprisinganticorrosion properties of the coating. Baking or curing at suchtemperatures is believed to result in the formation of a structure inthe resulting coating which is particularly resistant to corrosion.

According to a preferred embodiment, the anticorrosion coating resultsfrom an application operation involving, prior to a baking operation, adrying operation of the coated metallic parts, by supply of thermalenergy, such as by convection, infrared or induction, at a temperatureof between 30° C. and 250° C., preferably at a temperature of 70° C., inconvection or in infrared heating for 10 to 30 minutes on line or forapproximately 30 seconds to 5 minutes by induction heating. Beforecoating, it is judicious in the majority of cases to eliminate anyforeign matter from the surface of the substrate, especially by cleaningand careful degreasing. Under these conditions, the thickness of the drycoating film thus applied is between 3 μm (11 g/m²) and 30 μm (110 g/m²)and preferably between 4 μm (15 g/m²) and 12 μm (45 g/m²), moreparticularly between 5 μm (18 g/m²) and 10 μm (40 g/m²).

The present invention also extends to the metallic substrate, preferablyof steel or steel coated with zinc or with a base layer of zincdeposited by different application methods including mechanicaldeposition, to cast iron and aluminium, provided with an anticorrosioncoating according to the invention applied with the aid of thepreviously noted compositions.

The metallic substrate can be previously treated, for example by atreatment with chromate or with phosphate. Thus, the substrate can bepretreated in order to have, for example, a phosphate coating of iron ina quantity of 0.1 to 1 g/m² or a phosphate coating of zinc in a quantityof 1.5 to 4 g/m².

The present invention likewise relates to an aqueous composition ofC₁-C₈ tetraalkyl titanate and/or of C₁-C₈ tetraalkyl zirconate, intendedfor the preparation of a coating composition for a metallic substrate inaqueous dispersion, prepared from a water-soluble organic solvent, abinder containing a silane including at least one hydrolysable functionin hydroxyl function, a C₁-C₈ tetraalkyl titanate and/or zirconate andwater, in the following proportions (percentages by mass): from about 0%to about 20% water-soluble organic solvent; from about 20% to about 50%of silane-based binder; from about 5% to about 25% C₁-C₈ tetraalkyltitanate and/or zirconate; and from about 40% to about 70% water.

In the context of the present invention, that is to say when the silaneis found in the presence of C₁-C₈ tetraalkyl titanate and/or zirconate,it is believed that the silane, in hydrolysed form before condensation,is capable of reacting with the previously noted hydrated titanium oxideand/or zirconate in order to provide a partially stable polymeric chaincontaining silicon and titanium and/or zirconate atoms. The silane isbelieved to then stabilize the C₁-C₈ tetraalkyl titanate and/orzirconate. The chemical reactions can be expressed as follows:

(1) Hydrolysis of the Silane:R—Si(OR′)₃+3H₂O

R—Si(OH)₃+3R′OH(2) Conversion of the Organic Titanate or Zirconate to Hydrated Titaniumor Zirconium Oxide:X—(OR″)₄+4H₂O

X(OH)₄+4R″OH(3) Reaction Between the Hydrated Titanium or Zirconium Oxide and theHydrolysed Silane:2R—Si(OH)₃+X(OH)₄

X(OH)₂.2[R—SiO(OH)₂]

The silane and the organic titanate or zirconate thus associate in orderto form the following partial polymeric chain:X(OH)₂.2[R—SiO(OH)₂]

The reaction can continue and lead to the formation of a polymeric chainof the following formula (III):

in which X represents Ti or Zr.

The water-soluble organic solvent is preferably selected from the groupcomprising glycolic solvents such as the glycol ethers, in particulardiethylene glycol, triethylene glycol and dipropylene glycol, acetates,propylene glycol, alcohols, ketones, propylene glycol ether, as well astheir mixtures.

The silane including at least one hydrolysable function in hydroxylfunction contained in the binder is preferably selected from a C₁-C₄,and most preferably C₁-C₂, alkoxy radical. In addition, this silanepreferably includes an epoxy function. The noted silane is preferablychosen from di- or trimethoxysilane with an epoxy function and di- ortriethoxysilane with an epoxy function, as well as their mixtures, inparticular gamma-glycidoxypropyl-trimethoxysilane orbeta-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane.

The C₁-C₈ tetraalkyl titanate is preferably selected from the groupcomprising tetra-ethyl titanate (TET), tetra-n-butyl titanate (T_(n)BT)and octyleneglycol titanate (OGT) and the C₁-C₈ tetraalkyl zirconate isselected from the group comprising tetra-n-propyl zirconate andtetra-n-butyl zirconate. In the aqueous composition, the ratio by massof C₁-C₈ tetraalkyl titanate and/or zirconate with respect to the silaneis from about 60/40 to about 40/60, and preferably about 50/50.

The aqueous composition of C₁-C₈ tetraalkyl titanate and/or C₁-C₈tetraalkyl zirconate can be prepared by mixing the silane-based binder,the noted titanate or zirconate and, if necessary, the water-solubleorganic solvent, with a small quantity of water and then, by continuousprogressive addition, at a low rate, of the remaining quantity of water.

In this stabilized form, the C₁-C₈ tetraalkyl titanate and/or zirconatecan, for example, then be introduced into a coating composition for ametallic substrate in aqueous phase, especially an anticorrosion coatingcomposition based on particulate metal in aqueous dispersion, whilelimiting the formation of titanium dioxide.

The present invention also relates to the use of the aqueous compositionof C₁-C₈ tetraalkyl titanate and/or C₁-C₈ tetraalkyl zirconate definedabove in pretreatment for coatings or adhesives such as for examplevarious polyurethanes, acrylics, rubbers . . . . This composition canalso be used in post treatment applications as a sealer based onmetallic particles. This composition can likewise be used in passivationtreatments for substrates based on steel, zinc, aluminium or steelcovered with a zinc-based coating. This composition can also be used inan additive in order to improve the adhesion of the coatings oradhesives (polyurethane, acrylic, rubber, . . . ) in aqueous phase.

EXAMPLES

The examples described herein illustrate various manners in which thepresent invention can be employed, and do not limit the presentinvention in any fashion.

Preparation of Test Panels:

Unless indicated otherwise, the test panels are typically stainlesssteel panels with a low carbon content, laminated in the cold. They areprepared by immersion in a cleaning solution. Then, the panels are wipedwith a cleaning pad and then rinsed with water and again immersed in thecleaning solution. After removal of the solution, the panels are rinsedwith tap water and dried.

Application of the Coating to the Test Panels and Weight of the Coating:

The clean parts are coated, in a typical fashion, by dipping the partsinto the coating composition, by withdrawing the parts, and thendraining the excess composition. This process is repeated several timeswith a moderate stirring action. The coated parts are then immediatelybaked or dried at ambient temperature or pre-hardened at a moderatetemperature until the coating is dry to the touch and thus baked. Thecoating weights (mg/cm²) are determined by comparative weighing beforeand after coating.

Test of Resistance to Corrosion (ISO 9227) and Estimation:

The resistance to corrosion of coated parts is measured by means of astandard salt projection test (saline mist) for paints and varnishes,referred to as ISO 9227. In this test, the parts are placed in a chambermaintained at a constant temperature where they are exposed to a fineprojection (mist) of a 5% saline solution during specific periods oftime, rinsed with water and dried. The extent of corrosion of the partstested can be expressed in the form of the percentage of red rust.

Example 1 Composition Based on Organic Titanate Compatible in OrganicPhase

In this example, a preferred embodiment composition set forth in Table 1was prepared as described herein.

TABLE 1 Preferred Embodiment Composition Constituent Quantity (g/kg) DPG(dipropylene glycol) 170.60 R40⁵ 13.00 R95⁶ 14.00 Dry aluminium² 25.00Zinc paste¹ 245.00 Silane A-187³ 90.00 Dehydran¹⁰ 5.00 Sodium silicate⁴8.00 Boric acid 7.50 Molybdenum oxide⁹ 8.00 T_(n)BT (tetra-n-butyltitanate)⁸ 40.00 Kelzan⁷ 0.65 Water 373.30 ¹Zinc in the form of paste toapproximately 92% in white spirit ²Alu Chromal VIII powder marketed byEckart Werke ³γ-glycidoxypropyltrimethoxysilane (Crompton) ⁴sodiumsilicate (Rhodia) ^(5,6)Ethoxylated nonylphenol of R40 or of R95,supplier Oxiteno SA (Brazil) ⁷Kelzan/Rhodopol 23 from Rhodia ⁸SupplierDuPont de Nemours ⁹Supplier Lavollée ¹⁰Supplier Cognis SA

Example 2 Composition Based on Organic Titanate Compatible in OrganicPhase

In this example, another preferred embodiment composition set forth inTable 2 was prepared.

TABLE 2 Preferred Embodiment Composition Constituent Quantity (g/kg) DPG(dipropylene glycol) 175.60 R40 13.00 R95 14.00 Dry aluminium 10.00 Zincpaste 260.00 Silane A-187 115.00 Silicate H300 10.00 Boric acid 9.50Molybdenum oxide 10.00 T_(n)BT (tetra-n-butyl titanate) 60.00 Kelzan0.65 Water 317.25

The composition set forth in Table 2 was coated on various metal partsand then the coated parts heat cured as described herein. The results ofresistance to saline mist are set forth below in Table 3.

TABLE 3 Results of Tests of Resistance to Saline Mist Layer coatingweight Resistance to saline Duration of bath (days) (g/m²) mist (hours)5 23.6 2064 10 19.8 1944 15 20.1 1752

Example 3 Composition Based on Organic Titanate Compatible in OrganicPhase

Another preferred embodiment composition was formed as follows.

TABLE 4 Preferred Embodiment Composition Constituent Quantity (g/kg) DPG(dipropylene glycol) 153.50 R40 13.00 R95 14.00 Dry aluminium 10.00 Zincpaste 260.00 Silane A-187 95.00 Silicate H300 10.00 Boric acid 9.50Molybdenum oxide 10.00 TET (tetraethylene titanate)¹¹ 40.00 Kelzan 0.65Water 379.35 ¹¹supplied by DuPont de Nemours

The composition set forth in Table 4 was coated on various metal partsand then the coated parts heat cured as described herein. The results ofresistance to saline mist are set forth below in Table 5.

TABLE 5 Results of Tests of Resistance to Saline Mist Layer coatingweight Resistance to saline Duration of bath (days) (g/m²) mist (hours)5 20.8 456 10 19.7 360

Example 4 Process for Preparation of an Aqueous Composition ofTetrabutyl Titanate, Organic Titanate Compatible in Organic Phase

The following reagents are mixed in order:

a) 30.00 g of DPG (dipropylene glycol)

b) 50.00 g of silane A-187

c) 20.00 g of T_(n)BT (tetrabutyl titanate)

The solution obtained is allowed to stand for 24 hours. The silane,introduced into the DPG before the T_(n)BT, reacts with the wateroptionally present in the DPG. An uncontrolled reaction of the organictitanate with the water optionally present in the DPG is thus avoided.100.00 g of water (approximately 100.00 ml) are added respecting thefollowing procedure:

i) add 0.125 ml of water dropwise and then allow the solution to standfor 10 minutes;

ii) repeat step i) 5 times;

iii) add the remaining quantity of water at a rate of 0.25 ml ofwater/minute/3 pulses, or approximately 0.083 ml of water every 20seconds.

An aqueous composition of colorless organic titanate is obtained. Smallcrystals can appear. It is believed that these are silica crystals.

The total duration of the preparation of the aqueous composition oforganic titanate is approximately 7 h 30 min.

The aqueous composition of organic titanate is allowed to stand for atleast 24 hours before optionally being introduced into a composition ofanticorrosion coating.

Example 5 Process for Preparation of an Aqueous Composition of OrganicTitanate Compatible in Organic Phase

The process proceeds in the same fashion as in Example 4 except that thequantity of T_(n)BT introduced is 30.00 g. An aqueous composition ofcolorless or sometimes slightly yellow organic titanate is obtained.

Example 6 Process for Preparation of an Aqueous Composition of OrganicTitanate Compatible in Organic Phase

The process proceeds in the same fashion as in Example 4 except that thequantity of T_(n)BT introduced is 40.00 g. An aqueous composition ofcolorless or sometimes slightly yellow organic titanate is obtained.

Example 7 Process for Preparation of an Aqueous Composition of OrganicTitanate Compatible in Organic Phase

The process proceeds in the same fashion as in Example 4 except that thequantity of T_(n)BT introduced is 40.00 g and the quantity of silane A187 introduced is 70.00 g. An aqueous composition of colorless orsometimes slightly yellow organic titanate is obtained.

Example 8 Corrosion Resistance of a Coating Composition Based on OrganicTitanate Compatible in Organic Phase

The aqueous composition of organic titanate obtained in Example 6 isintroduced into an anticorrosion coating composition. Table 6 belowindicates the formulation of the composition thus obtained and that ofan anticorrosion coating composition of the prior art which does notcontain organic titanate.

TABLE 6 Preferred Embodiment Composition and Prior Art CompositionPreferred Embodiment Composition of the Composition A (g/kg) Prior Art B(g/kg) DPG 160.60 160.60 Silane A 187 90.00 90.00 Water 383.30 421.10Tetra-n-butyl titanate 40.00 — Dry aluminium 25.00 25.00 lamellae Zincpaste 245.00 245.00 Molybdenum oxide 8.00 10.00 R40 13.00 13.00 R9514.00 14.00 Dehydran 5.00 5.00 Sodium silicate 8.00 8.00 Boric acid 7.507.50 Kelzan 0.60 0.80

The characteristics of composition A are reported in Table 7 below:

TABLE 7 Characteristics of Preferred Embodiment Composition A DurationCoating % of of the bath Adhesion Appearance pH weight (g/m²) solidViscosity 72 hours excellent very good 7.7 1.35 36.1 54 s (23° C.) 5days excellent very good 7.9 1.36 37.0 64 s (23° C.) 10 days excellentvery good 8.1 1.39 38.3 70 s (26° C.) 15 days excellent very good 7.91.40 40.0 83 s (26° C.) 20 days excellent very good 7.8 1.42 41.9 121 s(25° C.)  25 days excellent very good 8.1 1.39 39.4 90 s (24° C.)

The resistance of the two compositions to the saline mist is compared.The resistance values to the saline mist measured are summarized inTable 8 below.

TABLE 8 Results of Tests of Resistance to Saline Mist PreferredEmbodiment Composition of the Composition A Prior Art B Resistance toResistance to Layer coating saline mist Layer coating saline mist weight(g/m²) (hours) weight (g/m²) (hours) 16 704 16 208 20 880 20 260 24 105624 312 28 1232 28 364 32 1408 32 416 36 1584 36 468

Satisfactory results for resistance to the saline mist are thus observedfor the coating composition according to the invention. In fact, for alayer coating weight of 24 g/m², it is possible to attain a duration ofresistance to the saline mist of greater than 1000 hours whereas for acomposition without organic titanate the duration of resistance to thesaline mist is only 312 hours. The addition of organic titanate allowsthe corrosion resistance of the coating to be at least tripled underthese conditions.

Example 9 Composition Based on Organic Titanate Compatible on OrganicPhase

The addition of small quantities of organic titanate (for example 10, 20or 30 g/kg) allows the quantity of silane and of molybdenum oxide to beintroduced to be decreased, which reduces costs, while conserving goodanticorrosion results.

In the following examples of additional preferred embodimentcompositions (Table 9), the quantity of silane is reduced to 44% byweight and the quantity of molybdenum oxide is reduced to 20% by weight,with respect to the quantities conventionally introduced intoanticorrosion coating compositions.

TABLE 9 Preferred Embodiment Compositions Composition C Composition DComposition E (g/kg) (g/kg) (g/kg) DPG 160.60 160.60 160.60 Silane A 18750.00 50.00 50.00 Water 453.20 443.20 433.20 Tetra-n-butyl 10.00 20.0030.00 titanate Dry aluminium 25.00 25.00 25.00 lamellae Zinc paste245.00 245.00 245.00 Molybdenum oxide 8.00 8.00 8.00 R40 13.00 13.0013.00 R95 14.00 14.00 14.00 Dehydran 5.00 5.00 5.00 Sodium silicate 8.008.00 8.00 Boric acid 7.50 7.50 7.50 Kelzan 0.70 0.70 0.70

The values of resistance to the saline mist measured are summarized inTable 10 below.

TABLE 10 Results of Tests of Resistance to Saline Mist Composition CComposition D Composition E Weight of layer (g/m²) 21 22.5 20.5 Red rust(number of 170 310 430 hours)

Example 10 Process of Introduction of Chelated Organic Titanates orZirconates, Compatible in Aqueous Phase, into an Aqueous Phase,Co-Hydrolysis with the Silane

A preferred embodiment composition comprising a titanate is prepared asfollows. An aqueous phase is prepared by combining 10 parts by weight ofTYZOR® TEP (supplied by DuPont de Nemours, 60% dry extract) and 25 partsby weight of silane A-187, and mixing with magnetic stirring for onehour. 113 parts by weight of water are then added rapidly and themagnetic stirring is maintained for one hour.

This mixture is then introduced into an aqueous composition of 350 partsby weight of water, 8.8 parts by weight of sodium silicate, 8.2 parts byweight of boric acid and 9 parts by weight of molybdenum oxide.

An organic phase is prepared by combining the components set forth inTable 11 as follows.

TABLE 11 Organic Phase Constituent Parts by Weight Dipropylene glycol 75Remcopal N4100¹² 14 Remcopal N9 1001¹³ 15.5 Silane A 187 70 Zinc paste235 Aluminium Stapa¹⁴ 30 Schwego foam 8325¹⁵ 5.5 Yttrium oxide¹⁶ 30Aerosil 380¹⁷ 0.4 ¹²wetting agent of ethoxylated nonylphenol type (CECA)¹³wetting agent of ethoxylated nonylphenol type (CECA) ¹⁴80% ChromalVIII in dipropylene glycol, marketed by Eckart Werke ¹⁵hydrocarbon-typeantifoam (Schwegman) ¹⁶Y₂O₃ of purity equal to 99.99%¹⁷anti-sedimentation agent of silica type (Degussa)

A preferred embodiment bath in accordance with the present invention wasprepared by mixing the previously noted aqueous phase and organic phase.

A reference bath was prepared by combining an aqueous phase as set forthin Table 12 with an organic phase.

TABLE 12 Aqueous Phase of Reference Composition Constituent Parts byWeight Water 463 Sodium silicate 20 N 32 8.8 Boric acid 8.2 Molybdenumoxide 9 Silane A 187 31

The organic phase of the reference composition has the same compositionas the organic phase of the previously noted preferred embodiment bathaccording to the invention (Table 11).

The saline mist tests are carried out after an ageing of the baths,according to the invention and reference, for 48 hours. The resultsobtained are given in Table 13 below:

TABLE 13 Results of Tests of Resistance to Saline Mist Results on screws(5^(d)/4.8^(e)) Results on steel support Such V + Sacrificial as CM^(a)2 × G^(b) protection^(c) 2 × G^(b) Reference Bath 672/672 456/840168/336 624 168 Preferred >1150 840/912 336/576 1150 744 Embodiment Bath^(a)V + CM: saline mist results after the screws had been subjected tothe mechanical shocks of vibrations and falls. ^(b)2 × G: saline mistresults after the screws or the plates had been subjected twice tochipping, that is to say a spattering of impacts. ^(c)Sacrificialprotection: number of hours of exposure to the saline mist, without redrust after incision of the coating to the metal. ^(d)notation 5: resultscorresponding to less than 1% of red rust on surface. ^(e)notation 4.8:results corresponding to less than 5% of red rust on surface.

Table 13 demonstrates that the introduction of chelated organictitanate, compatible in aqueous phase, co-hydrolysed with the silane inthe coating compositions increases the resistance to saline mist of thesamples treated by these compositions.

Example 11

The following evaluations were performed using a preferred embodimentcoating composition with an organic titanate compatible in organicphase, tetra-ethyl titanate. The coating composition is applied onscrews (two layers). The coated screws are then submitted to a heatingor curing step, namely:

Phase 1: 150° C. for 25 min

Phase 2: 180° C. for 25 min

Phase 3: 250° C. for 25 min

Phase 4: 330° C. for 15 min

After this heating step, the coated screws are exposed to saline mist orto atmospheric conditions. Upon observation, each sample was assigned agrade according to the following schedule set forth below in Table 14.

TABLE 14 Schedule of Rust Grades Grade “5” 0% red rust Grade “4” 1 to 5%red rust Grade “3” 5 to 15% red rust Grade “2” 15 to 25% red rust Grade“1” 25 to 50% red rust Grade “0” >50% red rust

The grade for each test item (evaluated after each heating temperature)is the mean value for 5 screws.

TABLE 15 Results of Tests of Resistance to Saline Mist Heating Layercoating Cohesion temperature weight (g/m²) 0-3 (max) Saline mist (hours)150° C. 27.1 3 72 h - grade 1 180° C. 26.5 3 72 h - grade 2 250° C. 24.33 72 h - grade 5 144 h - grade 4.4 330° C. 22.7 3 1032 h - grade 5  1152h - grade 4.8 

TABLE 16 Results of Tests of Resistance to Atmospheric ConditionsHeating temperature Saline mist (days) 150° C.  15 d - grade 4 180° C. 15 d - grade 5  20 d - grade 4.2 250° C. 118 d - grade 5 126 d - grade4.8 330° C. 146 d - grade 5

These results demonstrate that the coating composition must be heated toand preferably maintained at a sufficient temperature to provide aneffective anticorrosion action. The starting temperature, at which onestarts to observe a slight effect on anticorrosion, is 180° C. When thecoating composition is heated at higher temperatures, of 250° C. or 330°C., the anticorrosion properties are significantly improved. Preferably,the coating composition is maintained or held at such relatively hightemperatures for a period of from about 1 minute to several hours ormore, and more preferably from about 10 minutes to about 60 minutes whenusing convective heating or infrared heating. Significantly shorter timeperiods can be utilized when heating by other methods such as inductiveheating, such as from about 10 seconds to 10 minutes and preferably fromabout 30 seconds to 5 minutes.

Referring to FIG. 1, the infrared (IR) spectra was obtained of apreferred embodiment composition comprising a silane-based binder andheated at different temperatures: 70° C., 180° C., 250° C. and 310° C.From the IR spectra, it can be seen that the films heated at 70° C. and180° C. show peaks in common, and the resulting films heated at 250° C.and 310° C. show peaks in common. This suggests that the structure ofthe films heated at 70° C. and 180° C. are likely not significantlydifferent from one another. This also suggests that the structure of thefilms heated at 250° C. and 310° C. are likely not significantlydifferent from one another. However, the spectra of the films heated at70° C. and 180° C. as compared to those heated at 250° C. and 310° C.are significantly different as shown in FIG. 1. This suggests that thestructure of the films baked and/or cured at these temperatures are verydifferent from one another. This demonstrates that the heatingtemperature has a significant influence on the structure of theresulting coating layer or film. In addition, utilizing a baking orcuring temperature above 180° C. will also improve a coating comprisingaluminium or zinc flakes used in the composition of the invention. Ahigh curing temperature such as above 180° C., and preferably above 240°C., is needed to obtain coatings that exhibit significant anticorrosionproperties.

The preferred embodiment compositions are baked or cured to formanticorrosion coatings. Specifically, by baking the preferred embodimentcompositions at a temperature of at least above 180° C. and below 350°C., an organo-mineral tridimensional structure in the coating andbonding to the substrate are formed. This structure and bonding to thesubstrate are major factors which enable the resulting coating to serveas an anticorrosion coating. The preferred embodiment coatingcompositions when baked at temperatures within a range of greater than180° C. and up to 350° C. exhibit a resistance to saline mist such thatthe coatings can withstand exposure to saline mist for at least 200hours and preferably at least 250 hours, without formation andappearance of red rust. These characteristics are with regard tostandard application conditions and measured in accordance with thestandard salt projection test, ISO 9227.

Generally, a coating containing metal particles in an inorganic bindersuch as silane which is not baked at a temperature at least above 180°C. and below 350° C., does not confer anticorrosion properties. Such acoating will not exhibit a resistance to saline mist higher than 200 to250 hours without red rust, in standard application conditions andmeasured by means of the standard salt projection test ISO 9227, whichis clearly not sufficient for anticorrosion coatings.

Although not wishing to be bound to any particular theory, it isbelieved that it is believed that the lack of such resistance to salinemist is due to the lack of formation of a three-dimensional structure ofthe coating and/or bonding to the substrate which occurs if the coatingcomposition is not baked to an appropriate temperature, which is atleast above 180° C.

Many other benefits will no doubt become apparent from futureapplication and development of this technology.

All patents, published applications, industry standards and articlesnoted herein are hereby incorporated by reference in their entirety.

It will be understood that any one or more feature or component of oneembodiment described herein can be combined with one or more otherfeatures or components of another embodiment. Thus, the presentinvention includes any and all combinations of components or features ofthe embodiments described herein.

As described hereinabove, the present invention solves many problemsassociated with previously known compositions and practices. However, itwill be appreciated that various changes in the details, materials andarrangements of components and operations, which have been hereindescribed and illustrated in order to explain the nature of theinvention, may be made by those skilled in the art without departingfrom the principle and scope of the invention, as expressed in theappended claims.

What is claimed is:
 1. A method for forming a coated metallic substratehaving an anticorrosion coating, the method comprising: obtaining acoating composition including from 0.3% to 24% by weight of at least oneagent selected from the group consisting of organic titanate, organiczirconate and mixtures thereof, from 10% to 40% by weight of aparticulate metal or a mixture of particulate metals, at least 1% byweight of a silane-based binder, and water, wherein the sum of theorganic titanate and/or zirconate agent and of the silane-based binderis from 5 to 25% by weight; forming a coating layer of the coatingcomposition on a metallic substrate; and subjecting the coating layer toa baking operation at a temperature greater than 180° C. and up to 350°C. by supply of thermal energy to thereby form the anticorrosioncoating.
 2. The method of claim 1 wherein the metallic substrate isselected from the group consisting of steel, zinc-coated steel, steelcovered with a zinc-based coating, cast-iron, and aluminium.
 3. Themethod of claim 2 wherein the metallic substrate is steel covered with azinc-based coating.
 4. The method of claim 1 wherein (i) the organictitanate is selected from the group consisting of titanates compatiblein organic phase, titanates compatible in aqueous phase, andcombinations thereof, and (ii) the organic zirconate is selected fromthe group consisting of zirconates compatible in organic phase,zirconates compatible in aqueous phase, and combinations thereof.
 5. Themethod of claim 4 wherein the titanates compatible in organic phase areC₁-C₈ tetraalkyl titanates and the zirconates compatible in organicphase are C₁-C₈ tetraalkyl zirconates.
 6. The method of claim 5 whereinthe C₁-C₈ tetraalkyl titanates are selected from the group consisting oftetraethyl titanate, tetra-n-butyl titanate, octylene glycol titanateand combinations thereof.
 7. The method of claim 5 wherein the C₁-C₈tetraalkyl zirconates are selected from the group consisting oftetra-n-propyl zirconate, tetra-n-butyl zirconate, and combinationsthereof.
 8. The method of claim 4 wherein the titanates compatible inaqueous phase are chelated organic titanates, and the zirconatescompatible in aqueous phase are chelated organic zirconates.
 9. Themethod of claim 8 wherein the chelated organic titanates aretriethanolamine titanates.
 10. The method of claim 8 wherein thechelated organic zirconates are triethanolamine zirconates.
 11. Themethod of claim 1 wherein the particulate metal is selected from thegroup consisting of zinc, aluminium, zinc alloys, aluminium alloys, andcombinations thereof.
 12. The method of claim 11 wherein the alloysinclude metals selected from the group consisting of manganese,magnesium, tin, and combinations thereof.
 13. The method of claim 11wherein the alloys include a eutectic alloy of zinc and aluminium and atrace of rare earth elements.
 14. The method of claim 1 wherein thesilane-based binder comprises a silane having at least one hydrolysablehydroxyl function.
 15. The method of claim 14 wherein the hydrolysablehydroxyl function is a C₁-C₈ alkoxy radical.
 16. The method of claim 1wherein the silane includes an epoxy function.
 17. The method of claim 1wherein the silane is selected from the group consisting of di- ortrimethoxysilane with an epoxy function, di- or triethoxysilane with anepoxy function, and mixtures thereof.
 18. The method of claim 17 whereinthe trimethoxysilane is selected from the group consisting ofgamma-glycidoxypropyltrimethoxysilane,beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and mixtures thereof.19. The method of claim 1 wherein the coating composition furtherincludes an organic solvent or a mixture of organic solvents.
 20. Themethod of claim 19 wherein the organic solvent is selected from thegroup consisting of glycolic solvents, acetates, nitropropane, alcohols,ketones, white spirit, 2,2,4-trimethyl-1,3-pentanediol isobutyrate(texanol), and mixtures thereof.
 21. The method of claim 1 wherein thecoating composition further includes from 0.1 to 7% by weight ofmolybdenum oxide, with respect to the total weight of the composition.22. The method of claim 1 wherein the coating composition furtherincludes from 0.5 to 10% by weight, with respect to the total weight ofthe composition, of an anticorrosion reinforcing agent selected from thegroup consisting of yttrium, zirconium, lanthanum, cerium, praseodymium,in the form of oxides or of salts thereof.
 23. The method of claim 22wherein the reinforcing agent is Y₂O₃.
 24. The method of claim 1 whereinthe coating composition further includes from 0.2 to 4% by weight, withrespect to the total weight of the composition, of a corrosion inhibitorpigment.
 25. The method of claim 24 wherein the corrosion inhibitorpigment is aluminium triphosphate.
 26. The method of claim 1 wherein thecoating composition further comprises an agent selected from the groupconsisting of a thickening agent, a wetting agent, and combinationsthereof.
 27. The method of claim 26 wherein the thickening agent ispresent in an amount of 0.005 to 7% by weight with respect to the totalweight of the coating composition.
 28. The method of claim 26 whereinthe wetting agent is present in an amount of 0.1 to 4% by weight withrespect to the total weight of the coating composition.
 29. The methodof claim 1 wherein the baking operation by supply of thermal energyincludes at least one of convection, infrared, and induction.
 30. Themethod of claim 1 wherein the baking operation is performed for 10 to 60minutes by convection or infrared.
 31. The method of claim 1 wherein thebaking operation is performed for 30 seconds to 5 minutes by induction.32. The method of claim 1 wherein prior to the baking operation thecoated layer is subjected to a drying operation by supply of thermalenergy.
 33. The method of claim 32 wherein the drying operation bysupply of thermal energy includes at least one of convection, infrared,and induction.
 34. The method of claim 33 wherein the drying operationis performed at a temperature of between 30 and 250° C.
 35. The methodof claim 33 wherein the drying operation is performed by convection orinfrared for 10 to 30 minutes on line.
 36. The method of claim 33wherein the drying operation is performed for 30 seconds to 5 minutes byinduction.
 37. The method of claim 1 wherein the anticorrosion coatinghas a thickness of the dry film between 3 μm (11 g/m²) and 30 μm (110g/m²).
 38. The method of claim 37 wherein the thickness is between 4 μm(15 g/m²) and 12 μm (45 g/m²).
 39. The method of claim 38 wherein thethickness is between 5 μm (18 g/m²) and 10 μm (40 g/m²).
 40. The methodof claim 1 wherein the baking operation is performed at a temperature ofbetween 240° C. and 350° C.
 41. The method of claim 40 wherein thebaking operation is performed at a temperature of between 240° C. and330° C.
 42. The method of claim 1 wherein forming the coating layer ofthe coating composition on a metallic substrate is performed by one ofspraying, soaking-draining, and soaking-centrifugation.
 43. The methodof claim 1 wherein the anticorrosion coating exhibits resistance tocorrosion from exposure to saline mist for at least 200 hours withoutformation of red rust.